It's about context and its place in time.I find your comments interesting in light of the fact that only 6 Prime Ministers in Canadian history have served a longer consecutive term than JT. Even some Prime Ministers who have served more years in office have done so non-consecutive occasions. It's like the electorate gets tired of the ruling party and wants a change, regardless of political philosophy.
Harper served almost 10 years and helped Canada crawl out of a devastating recession. However, even that couldn't erase the impact it had on Canadians.
Trudeau was the perfect candidate that the Liberals offered. He had the name. He was young. And he resonated with young voters who had come of age by the time he was elected. Everyone was quick to forgive him for scandals as long as they saw a future with him as the leader.
Almost 10 years later, those same young voters are in their late 20's/early 30's and have realized they were sold a lie. Their pay goes to taxes that are squandered. Life is unaffordable. They've realized what printing money & government debt translates into. They're pissed.
It will take a decade to fix what the Liberals have done but change needs to start somewhere.